Merge pull request #65 from saphid/fix/server-stdin-abort

A stop signal no longer crashes the server, and the app restarts it by itself

app/main.js

@@ -149,7 +149,7 @@ async function startServer() {
   const target = `http://127.0.0.1:${port}/`;
   for (let i = 0; i < 100; i++) {
     if (exited !== null) throw new Error(`The server exited (${exited}). See ${LOG}.`);
-    if (await ping(target)) { url = target; return; }
+    if (await ping(target)) { url = target; serverStarted = Date.now(); return; }
     await new Promise((r) => setTimeout(r, 100));
   }
   if (server === child) server = null;
@@ -175,18 +175,27 @@ function stopServer() {
   if (server) endServer(server);
 }
 
-function errorPage(message) {
+function errorPage(message, title = "Frame Control couldn't start") {
   const esc = (s) => s.replace(/[&<>]/g, (c) => ({ "&": "&amp;", "<": "&lt;", ">": "&gt;" }[c]));
   const html = `<!doctype html><meta charset="utf-8"><body style="margin:0;height:100vh;display:grid;
     place-items:center;background:${BG};color:#e6edf3;font:14px -apple-system,sans-serif">
-    <div style="max-width:560px;padding:32px;line-height:1.5"><h2>Frame Control couldn't start</h2>
-    <p>${esc(message)}</p><p style="color:#8b98a8">Fix it, then choose Frame → Restart Server.</p></div>`;
+    <div style="max-width:560px;padding:32px;line-height:1.5"><h2>${esc(title)}</h2>
+    <p>${esc(message)}</p>
+    <p><button onclick="this.disabled = true; frameApp.restartServer()" style="font:inherit;padding:6px 16px;
+      border-radius:6px;border:1px solid #30363d;background:#21262d;color:inherit;cursor:pointer">Try Again</button></p>
+    <p style="color:#8b98a8">Frame → Restart Server does the same.</p></div>`;
   return "data:text/html;charset=utf-8," + encodeURIComponent(html);
 }
 
+// A server that had been running starts again by itself (something stopped it: a
+// signal, a crash). One that stops again within a minute shows the error instead,
+// so a server that can't stay up doesn't restart forever.
+let serverStarted = 0;
 function serverDied(why) {
   url = null;
-  if (win) win.loadURL(errorPage(`The server stopped unexpectedly (${why}). See ${LOG}.`));
+  if (!win) return;
+  if (Date.now() - serverStarted > 60000) restartServer();
+  else win.loadURL(errorPage(`Its server stopped unexpectedly (${why}). See ${LOG}.`, "Frame Control stopped"));
 }
 
 // Restarts that overlap share one: two could each start a server, and the one
@@ -263,6 +272,11 @@ function fromUi(e) {
   } catch { return false; }
 }
 
+// The error page's Try Again button. The error page is the only data: page the window
+// shows (`url` can still be set then: the server answered but the page failed to load).
+ipcMain.handle("server:restart", (e) => {
+  if (win && e.sender === win.webContents && e.senderFrame && e.senderFrame.url.startsWith("data:")) restartServer();
+});
 ipcMain.handle("clipboard:read", (e) => fromUi(e) ? clipboard.readText() : "");
 // A PNG or JPEG (a screenshot) onto the clipboard as an image.
 ipcMain.handle("clipboard:writeImage", (e, bytes) => {

app/preload.js

@@ -14,6 +14,7 @@ contextBridge.exposeInMainWorld("frameApp", {
   readClipboard: () => ipcRenderer.invoke("clipboard:read"),
   writeImage: (bytes) => ipcRenderer.invoke("clipboard:writeImage", bytes),
   setUpConnection: () => ipcRenderer.invoke("connection:setup"),
+  restartServer: () => ipcRenderer.invoke("server:restart"),  // the "couldn't start" page's Try Again
   // The Frame menu's headset switcher: the page tells it the headsets, and hears picks.
   devicesChanged: (list) => ipcRenderer.send("devices:changed", list),
   onUseDevice: (cb) => {

tests/test_server.py

@@ -285,6 +285,18 @@ class OneServer(unittest.TestCase):
         r = conn.getresponse()
         self.assertEqual(r.status, 403, r.read())
 
+    @unittest.skipIf(os.name == "nt", "no SIGTERM on Windows")
+    def test_sigterm_while_the_app_holds_stdin_exits_cleanly(self):
+        """The app keeps stdin open; a stop signal used to abort Python (SIGABRT) at exit."""
+        env = {**os.environ, "FRAME_CONTROL_DATA_DIR": tempfile.mkdtemp(prefix="frame-one-server-"),
+               "FRAME_ALIAS": "frame-control-test.invalid"}
+        proc = subprocess.Popen([sys.executable, str(ROOT / "ui" / "server.py"), "--port", "0", "--exit-on-eof"],
+                                env=env, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, text=True)
+        self.addCleanup(lambda: (proc.stdin.close(), proc.stdout.close()))
+        self.assertIn("Frame Control on", proc.stdout.readline())
+        proc.terminate()
+        self.assertEqual(proc.wait(30), 0, proc.stdout.read())
+
 
 class ArtworkSettings(unittest.TestCase):
     """The settings panel's endpoints, with and without the page's X-Frame-UI key."""

ui/server.py

@@ -2667,12 +2667,16 @@ def main():
         signal.signal(signal.SIGTERM, lambda *_: (_ for _ in ()).throw(KeyboardInterrupt))
     if args.exit_on_eof:
         def watch_stdin():
-            sys.stdin.buffer.read()
+            # os.read, not sys.stdin.buffer.read: a buffered read holds stdin's lock,
+            # and if a signal stops the server first, Python aborts (SIGABRT) at exit
+            # when it can't take that lock back from this thread.
+            while os.read(0, 4096):
+                pass
             threading.Thread(target=httpd.shutdown, daemon=True).start()
         threading.Thread(target=watch_stdin, daemon=True).start()
-    # The real port, which --port 0 leaves to the system (the iPhone app reads it from here).
-    print(f"Frame Control on http://127.0.0.1:{httpd.server_address[1]}  (alias: {FRAME}; Ctrl-C to stop)", flush=True)
     try:
+        # The real port, which --port 0 leaves to the system (the iPhone app reads it from here).
+        print(f"Frame Control on http://127.0.0.1:{httpd.server_address[1]}  (alias: {FRAME}; Ctrl-C to stop)", flush=True)
         httpd.serve_forever()
     except KeyboardInterrupt:
         pass